1. Field of Invention
This invention relates to a new control system for tuck-in selvedge forming devices in a loom, in particular a loom for terry cloth formed by varying the reed beat-up position which, by enabling a single command to automatically prevent the cut warp ends from being tucked into the shed for a predetermined number of reed beat-ups with the loom in operation, achieved by locking in their rest position the tuck-in members of all said tuck-in selvedge forming devices or selvedge formers of the loom, independently of the type of selvedge former used and hence also enabling positively controlled conjugate-cam selvedge formers to be used, enables the higher operating speeds currently required of modern terry looms to be achieved, together with considerable mechanical simplification of the loom.
2. Description of the Related Art
From the state of the art, various systems are already known for controlling the members of selvedge formers for terry looms of the type using different reed beat-up positions.
In said known selvedge formers, the members for tucking the cut weft ends into the shed at each reed beat-up or after a predetermined number of reed beat-ups generally consist, for each selvedge former, of a weft tuck-in hook and a movable member or foot for weft gripping and cutting, both undergoing rotation and translation or axial movement.
Said movements of the hook or foot are achieved independently of each other by separate operating cams which are keyed onto a single drive shaft rotated continuously by the main loom shaft and move corresponding spring-loaded operating levers pivoted at one end onto a single shaft.
The controlled prevention of tuck-in of the cut weft ends into the shed for a predetermined number of reed beat-ups is achieved by a system which locks both the rotation of the hook and the rotation and translation of the foot substantially by a movement selection mechanism present on each selvedge former, in which appendices or teeth protecting from said operating levers cooperate with corresponding stops mounted on a spring-loaded support shaft which by means of an electromagnet is movable axially parallel to said single pivoting shaft for said operating levers from a position retained by said loading spring, in which said stops engage said teeth, into a position in which they are not engaged so that the weft end is inserted at each reed beat-up. In this manner, to achieve continuous operation of all the movable members of the selvedge former and hence the continuous tuck-in of the cut weft ends into the shed to form the selvedge, it is necessary merely to energize said electromagnet which, by overcoming the action of said loading spring, moves the stops on the shaft out of interference with said teeth of the operating levers.
According to another known method, all movement by electromagnetic action is dispensed with in the movement selection mechanism, the electromagnet being used only to retain against itself, when energized, an element which has been brought into contact with it mechanically.
In other words, a bridge frame is made to rock, by the action of a feeler rigid with it and cooperating via a spring with one of said operational control cams, from a position in which its bridge interacts with said stops or teeth projecting from said operating levers to lock said levers in position, to a position in which there is no longer interaction and in correspondence with which a metal armature rigid with said feeler rests against an electromagnet which, if energized, retains it.
Again in this case said movable members of the selvedge former, ie the weft tuck-in hook and the weft gripping and cutting foot, remain locked and inactive until said electromagnet is energized, which by retaining against itself the armature and hence the frame, enables said operating levers to follow the pattern of their operating cams to hence move said movable members.
Said methods have however the drawback of requiring a multiplicity of mechanisms for selecting the movement of the movable members of the selvedge former, given that each selvedge former must have its own, and the practical difficulty of achieving the high operating speeds possible with positive conjugate-cam selvedge formers, in that the need to lock certain of said operating levers in position categorically prevents these latter being able to be positively moved by conjugate cams.